A number of experimental animal cancers and human cancers have been shown to have high levels of one or both of two intracellular binding proteins which bind vitamin A alcohol (retinol) and vitamin A acid (retinoic acid). The levels are considerably higher than observed for the grossly normal tissue adjacent to the tumors. This elevation in level appears to be a tumor marker in some systems. Consequently, this project plans to use immunocytochemical localization of these proteins to detect tumor foci during carcinogenesis in several well defined rat systems. Antibodies to these proteins isolated from human tissue will be produced and the techniques will then be extended to human tissue and cancers with the goal of being able to identify tumor foci as well as suggest candidates for retinoid therapy. Further, target cell uptake of retinol from the blood transport protein RBP requires a specific plasma membrane receptor. The uptake process will be studied in cells in culture using purified RBP and [3H]retinol. The RBP-receptor interaction will be examined in vitro with membrane preparations and solubilized receptor. Possible interactions with cellular retinol binding protein (CRBP) will be examined. Attempts will be made to purify the receptor and to compare its presence/function in normal and neoplastic tissue.